GAS OVEN

Abstract: The invention relates to gas ovens. In particular, the invention relates to a gas oven for use in a stackable, multi-deck system, wherein each individual gas oven comprises a first burner unit (1) for providing heat to a top part of the oven and second burner units (2-9) for providing heat to a bottom part of the oven. In the gas oven described, the first burner unit (1) acts as a cross lighter for the second burner units (2-9) and during a warm up phase the first burner unit (1) operates in conjunction with the second burner units (2-9), whereas during a normal operating phase, the first burner unit (1) may operate on its own.

Description: GAS OVEN The invention relates to gas ovens. In commercial multi deck baking ovens, a very close control of operating top and bottom heat input is required. Hitherto, commercial multi deck ovens have been predominantly electric, as it was found that the gas ovens available could not provide controllable top and bottom heat, with a sufficient degree of uniformity throughout the oven. Preferred embodiments of the invention, aim to provide a gas oven having a high degree of temperature control. According to a first aspect of the invention, a gas oven is provided comprising a first burner unit for providing heat to a top part of the oven, and a second burner unit for providing heat to a bottom part of the oven. Preferably, the first and second burner units comprise a plurality of top and bottom burners. Preferably, the top and bottom burners are ribbon burners. Preferably, the second burner unit is situated beneath a sole tile, which sole tile forms a bottom part of an oven chamber. Preferably, the bottom burners are distributed at intervals beneath the sole tile, across the depth of the oven chamber. Preferably, the first burner unit acts as an ignition source for the second burner unit. The first burner unit is preferably two single units situated within a combustion area behind the side walls of the oven chamber. Preferably, the first burner unit is operable independently of the second burner unit. The second burner unit may not be able to operate independently of the first burner unit however. Whilst the second burner unit may be inhibited from functioning without operation of the first burner unit, it should be understood that heat output of the first and second burner units may be independently regulated. Preferably, heat output from the first burner unit is channelled behind the side wall of the oven chamber and over a top portion of the oven chamber. The heat may be channelled over the top portion of the oven chamber by means of a plurality of heat radiant tubes. Baffles may be provided within the radiant tubes so as to alter the pattern of heat distribution over the top portion of the oven chamber. Gases and products of combustion from the first and second burner units may be substantially isolated from the oven chamber. Preferably, following passage of heated gases and products of combustion over the top of the oven chamber, the gases and products of combustion are channelled via the oven chamber into an exhaust flue. Preferably, the exhaust flue is situated centrally above the oven chamber. The side walls of the oven chamber may be insulated from the combustion area by thermal insulation. Preferably, a temperature probe is provided having a temperature sensor to monitor oven chamber temperatures. Preferably, the gas oven is modular such that a plurality of the gas ovens are stackable, one above the other. Preferably, the exhaust flue of each individual gas oven is designed such that, when a plurality of gas ovens are stacked one above the other, a common exhaust flue is thereby formed. According to a second aspect of the invention, a method of operating a gas oven is provided, the method comprising: during a warm up phase operating a first burner unit together with a second burner unit; and during a normal operating phase, operating the first burner unit. Preferably, the second burner unit comprises a plurality of bottom burners. Preferably, the top and bottom burners are ribbon burners. Preferably, the second burner unit is situated beneath a sole tile, which sole tile forms a bottom part of an oven chamber. Preferably, the bottom burners are distributed at intervals beneath the sole tile, across the depth of the oven chamber. Preferably, during an ignition stage, ignition of the first burner unit serves to ignite the second burner unit. The first burner unit is preferably two single units situated within a combustion area behind the side walls of the oven chamber. The first and second burner units are preferably separately controllable, and when required both burner units may be operated simultaneously. Preferably, the first burner unit is controllable independently of the second burner unit. Preferably, the second burner unit is not operable independently of the first burner unit. By way of example, a specific embodiment of the present invention will now be described, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a schematic cross-sectional front end view of an embodiment of a gas oven according to the present invention as viewed along sectional lines A-A of Figure 4; Figure 2 is a schematic cross-sectional side view of the gas oven of Figure 1 as viewed along sectional lines B-B of Figure 1; Figure 3 is a schematic cross-sectional plan view of a bottom portion of the gas oven of Figures 1 and 2 as viewed along sectional lines C-C of Figure 1; Figure 4 is a schematic cross-sectional plan view of a top portion of the gas oven of Figures 1, 2 and 3, as viewed along sectional lines D-D of Figure 1; and Figure 5 is a view of a typical front control panel for the oven of Figures 1 to 4. Referring to Figures l to 4, a gas oven is illustrated comprising a pair of top burner units l and a plurality of ribbon burners 2 to 9. The ribbon burners 2 to 9 together form a bottom burner unit. The ribbon burners 2 to 9 are fed by injector units 10, 11 which provide a combustible gas/air mixture. Each of the ribbon burners 2 to 9 are also connected to the top burners 1, which act as cross-lighters for the bottom burner unit. Inside the oven, there is provided an oven chamber 12 in to which goods to be baked may be placed. The bottom of the oven chamber 12 is formed by a sole tile 13. The sole tile 13 typically comprises a ceramic tiling unit, the heat conductive properties of which are chosen so that once the sole tile 13 has been heated up by the bottom burner, the tile 13 will retain the heat, and only change temperature very slowly. The top burners 1 are situated to the side of the oven chamber 12, and have a combustion area 15. This combustion area 15 connects with radiant tubes 16 to 27. During baking, products give out moisture which needs to be exhausted. This is discharged with the products of combustion, through the exhaust channel 29. An outlet end of the radiant tubes 16 to 27 discharges via the oven chamber 12 into the exhaust channel 29 which connects with an exhaust flue 30. In situations where multiple numbers of ovens are stacked one above the other, the exhaust flues 30 of each individual oven are shared. The oven chamber 12 is accessible through an oven door 31. Air temperatures within the oven chamber 12 can be monitored via a temperature probe 14. Thermal insulation is provided around the oven, and in particular, insulating material 33, 34 is provided around the combustion area 15 so as to avoid over heating down the sides of the oven chamber 12. Figure 5 shows a possible front control panel configuration for the oven. The control panel comprises a temperature controller 37 and indicator 37a and two temperature control knobs 3S, 39. Knob 38 controls the top burner 1 and knob 39 controls the bottom burner 2. The knobs are calibrated in percentage heat input on a time basis. A typical operating sequence of the oven shown in Figures 1 to 4 will now be described. During a warm up phase, the top burners are provided with a combustible mixture of gas and air and ignited. The bottom burner unit, comprising ribbon burner units 2 to 9 is also provided with a combustible mixture of gas and air at this stage, and this mixture is ignited by the top burner 1. In this manner, the top burner 1 acts as a cross-lighter for the ribbon burners 2 to 9. Both the top and bottom burners are maintained in operation until a desired oven chamber temperature is achieved. The temperature of the oven chamber 12 is determined by a temperature sensor 14. Once the required temperature has been achieved, the top and bottom burner units operate on a percentage time basis determined by the top and bottom heat input settings. At some stages during the process the bottom burner 2 may be required to operate, but such operation would always take place in conjunction with operation of the top burner 1. Upon obtaining the correct temperature, the product to be baked is put into the oven chamber 12 through the oven door 31. A typical product for baking in the oven might be a pizza, tea cakes or bread for instance. All products during baking emit steam which needs to be exhausted. This steam is allowed to escape through the openings 42, 43, 44, 45, 46 & 47 and exhaust channel 29. In addition to this natural steam which is given off, some products actually require the introduction of extra steam into the oven chamber 12 during a process known as "steaming". This process gives a shine to the product. During steaming steam is channelled into the oven chamber from a source (not shown) . In order to avoid steam pressure from the source actually extinguishing the burners the exhaust channel and radiant tubes must be - 3 - temporarily isolated or shielded from the effects of the steam. During the process of cooking, oven chamber temperature monitored by the sensor 14 is displayed on the front wall of the oven, and the burners are thermostatically controlled,by means of temperature controller 37, control knobs 38, 39 and sensor 14. The top control knob 38 controls the top burner 1 and the bottom control knob 39 controls the bottom burner 2. Both knobs 38, 39 are calibrated in percentage heat input settings. Temperature controller 37 displays desired oven temperature and indicator 37a shows actual oven chamber temperature, as detected by sensor 14. In practice, due to the thermal properties of the sole tile 13, once the oven is at operating temperature the correct oven chamber temperatures can be maintained by the top burner 1 alone. Occasionally however, such as during periods when the oven door 31 has been opened, the bottom burner 2 may fire up to maintain the tile temperature. The operation of the burners and disposal of products of combustion will now be described. The ribbon burners 2 to 9 are supplied with a combustible mixture of gas and air via injector units 10 and 11. Similarly, the top burner unit 1 is provided with a combustible mixture from injector units 33, 48. Secondary air for aiding combustion of the ribbon burners 2 to 9 is drawn in through an aperture 36 in the front face of the oven. Exhaust products from the ribbon burners 2 to 9, along with heat and exhaust products from burner 1 are drawn up the sides of the oven chamber 12 through the combustion area 15. In the combustion area 15 temperatures are very high, and to avoid hot spots at the sides of the oven chamber 12 it is necessary to provide extra thermal insulation 33, 34. The waste products from the burners are then drawn into the radiant tubes 16 to 27 above the sides of the oven chamber 12. Again, because the exhaust products are extremely hot at this point, means are required for moderating the temperature at the sides of the oven chamber 12 and by initially channelling the exhaust products through radiant tubes 16 to 27, a degree of temperature moderation is achieved. Once the end region of each of the radiant tubes 16 to 27 has been reached, the exhaust products are discharged into the oven chamber 12, passing through ports 42-47 to be channelled back through exhaust channel 29 until they join the exhaust flue 30, whereupon they are expelled. The exhaust flue 30 runs substantially vertically and extends across the back of the oven. . In this manner, if decks are stacked one on top of another, they may share a common exhaust flue. The apparatus of the present invention provides a very effective means of providing a controllable gas oven, in which a high degree of uniformity of heat distribution within an oven chamber can be achieved. Using gas as a fuel is currently very cost effective. It is therefore possible with the gas oven of the present invention, to provide a relatively cheap yet highly controllable gas oven. Due to the controllability of the gas oven of the present invention, high quality baked products are achievable. The gas oven of the present invention, is a very compact unit and designed with ease of stacking in mind. Multideck units are therefore readily achievable. Although the front control panel is described as having knobs calibrated in percentage heat input, it will of course be readily apparent that they may be calibrated otherwise and, for instance, they may simply be marked in gas mark settings to directly control heat outputs of the burners. It will be appreciated that other variations such as varying burner numbers and positioning, varying temperature sensor positioning etc. may be carried out by a man skilled in the art without departing from the scope of the invention. The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings) , and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) , may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. The invention is not restricted to the details of the foregoing embodiment(s) . The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings) , or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims: CLAIMS 1. A gas oven comprising a first burner unit for providing heat to a top part of the oven, and a second burner unit for providing heat to a bottom part of the oven. 2. An oven according to claim 1, wherein the first and second burner units comprise a plurality of top and bottom burners. 3. An oven according to claim 2, wherein the top and bottom burners are ribbon burners. 4. An oven according to any of the preceding claims, wherein the second burner unit is situated beneath a sole tile, which sole tile forms a bottom part of an oven chamber. 5. An oven according to claim 4, wherein the bottom burners are distributed at intervals beneath the sole tile, across the depth of the oven chamber. 6. An oven according to any of the preceding claims, wherein the first burner unit acts as an ignition source for the second burner unit. 7. An oven according to any of the preceding claims, wherein the first burner unit comprises two single units situated within a combustion area behind the side walls of the oven chamber. 8. An oven according to any of the preceding claims, wherein the first burner unit is operable independently of the second burner unit. 9. An oven according to any of the preceding claims, wherein the second burner unit is not able to operate independently of the first burner unit. 10. An oven according to any of the preceding claims, wherein heat outputs of the first and second burner units are independently regulated. 11. An oven unit according to any of the preceding claims, wherein heat output from the first burner unit is channelled behind the side wall of the oven chamber and over a top portion of the oven chamber. 12. An oven according to claim 11, wherein the heat is channelled over the top portion of the oven chamber by means of a plurality of heat radiant tubes. 13. An oven according tc claim 12, wherein baffles are provided within the radiant tubes so as to alter the pattern of heat distribution over the top portion of the oven chamber. 14. An oven according to any of claims 11, 12 or 13, wherein heated gases and products of combustion pass over the top of the oven chamber are then channelled via the oven chamber into an exhaust flue. 15. An oven according to claim 14, wherein the exhaust flue is situated centrally above the oven chamber. 16. An oven according to any of the preceding claims, wherein side walls of the oven chamber are insulated from the combustion area by thermal insulation. 17. An oven according to any of the preceding claims, wherein a temperature probe is provided having a temperature sensor to monitor chamber temperatures. 18. An oven according to any of the preceding claims, wherein the oven is modular such that a plurality of such ovens are stackable, one above the other. 19. An oven according to claim 18, wherein the exhaust flue of each individual gas oven is designed such that, when a plurality of ovens are stacked one above the other, a common exhaust flue is thereby formed. 20. A method of operating a gas oven, the method comprising: during a warm up phase operating a first burner unit together with a second burner unit; and during a nor ai operating phase, operating the first burner unit. 21. A method according to claim 20, wherein the second burner unit comprises a plurality of bottom burners. 22. A method according to claim 20, or claim 21, wherein the top and bottom burners are ribbon burners. 23. A method according to claim 20, 21 or 22, wherein the second burner unit is situated beneath a sole tile, which sole tile forms a bottom part of an oven chamber. 24. A method according to claim 23, wherein the bottom burners are distributed at intervals beneath the sole tile, across the depth of the oven chamber. 25. A method according to any of claims 20 to 24, wherein during an ignition stage, ignition of the first burner unit serves to ignite the second burner unit. 26. A method according to any of claims 20 to 25, wherein the first burner unit comprises two single units situated within a combustion area behind the side walls of the oven chamber. 27. A method according to any of claims 20 to 26, wherein the first and second burner units are separately controllable, and when required both burner units may be operated simultaneously. 28. A method according to any of claims 20 to 27, wherein the first burner unit is controllable independently of the second burner unit. 29. A method according tc any of claims 20 to 28, wherein the second burner unit is not operable independently of the first burner unit.

Inventors: DOHREN DAVID GEORGE, MCSTRAFICK PAUL, DOHREN, DAVID, GEORGE, MCSTRAFICK, PAUL
Applicants: DOHREN DAVID GEORGE, MCSTRAFICK PAUL, TOM CHANDLEY LIMITED, DOHREN, DAVID, GEORGE, MCSTRAFICK, PAUL
Application year: 1994
Main classification: F24C3
IPC codes: A21B1, F24C3